Auto-injector

ABSTRACT

According to the invention, an auto-injector for administering a dose of a liquid medicament (M) comprises of a substantially cylindrical housing arranged to contain a pre-filled syringe filled with the medicament (M), a needle shroud slidably arranged with respect to the housing and adapted to rest on the skin of a patient receiving an injection, a releasable drive means arranged within the housing that is capable of, upon release, translating the needle shroud in a proximal direction (P) towards a safe position (PS) and a rotating collar rotatably arranged within the housing. The needle shroud in the safe position (PS) surrounds the injection needle after the injection has been carried out. The rotating collar engages the needle shroud in a manner that forces the rotating collar to rotate within the housing when the needle shroud is translated in the proximal direction (P).

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a a continuation of U.S. patent applicationSer. No. 16/909,107, filed on Jun. 23, 2020, which is a continuation ofU.S. patent application Ser. No. 15/669,571, filed on Aug. 4, 2017, nowU.S. Pat. No. 10,729,853, which is a continuation of U.S. patentapplication Ser. No. 13/993,528, with a 371 filing date of Jun. 12,2013, now U.S. Pat. No. 9,724,472, which is a U.S. National PhaseApplication pursuant to 35 U.S.C. § 371 of International Application No.PCT/EP2011/073502 filed Dec. 21, 2011, which claims priority to EuropeanPatent Application No. 10196067.2 filed Dec. 21, 2010, and U.S.Provisional Patent Application No. 61/432,255, filed Jan. 13, 2011. Theentire disclosure contents of these applications are herewithincorporated by reference into the present application.

TECHNICAL FIELD

The invention relates to an auto-injector for administering a dose of aliquid medicament.

BACKGROUND

Administering an injection is a process which presents a number of risksand challenges for users and healthcare professionals, both mental andphysical.

Injection devices (i.e. devices capable of delivering medicaments from amedication container) typically fall into two categories—manual devicesand auto-injectors.

In a manual device—the user must provide the mechanical energy to drivethe fluid through the needle. This is typically done by some form ofbutton/plunger that has to be continuously pressed by the user duringthe injection. There are numerous disadvantages to the user from thisapproach. If the user stops pressing the button/plunger then theinjection will also stop. This means that the user can deliver anunderdose if the device is not used properly (i.e. the plunger is notfully pressed to its end position). Injection forces may be too high forthe user, in particular if the patient is elderly or has dexterityproblems.

The extension of the button/plunger may be too great. Thus it can beinconvenient for the user to reach a fully extended button. Thecombination of injection force and button extension can causetrembling/shaking of the hand which in turn increases discomfort as theinserted needle moves.

Auto-injector devices aim to make self-administration of injectedtherapies easier for patients. Current therapies delivered by means ofself-administered injections include drugs for diabetes (both insulinand newer GLP-1 class drugs), migraine, hormone therapies,anticoagulants etc.

Auto-injectors are devices which completely or partially replaceactivities involved in parenteral drug delivery from standard syringes.These activities may include removal of a protective syringe cap,insertion of a needle into a patient's skin, injection of themedicament, removal of the needle, shielding of the needle andpreventing reuse of the device. This overcomes many of the disadvantagesof manual devices. Injection forces/button extension, hand-shaking andthe likelihood of delivering an incomplete dose are reduced. Triggeringmay be performed by numerous means, for example a trigger button or theaction of the needle reaching its injection depth. In some devices theenergy to deliver the fluid is provided by a spring.

US 2002/0095120 A1 discloses an automatic injection device whichautomatically injects a pre-measured quantity of fluid medicine when atension spring is released. The tension spring moves an ampoule and theinjection needle from a storage position to a deployed position when itis released. The content of the ampoule is thereafter expelled by thetension spring forcing a piston forward inside the ampoule. After thefluid medicine has been injected, torsion stored in the tension springis released and the injection needle is automatically retracted back toits original storage position.

SUMMARY

It is an object of the present invention to provide an improvedauto-injector.

The object is achieved by an auto-injector according to claim 1.

Preferred embodiments of the invention are given in the dependentclaims.

In the context of this specification, the terms distal and proximal aredefined from the point of view of a person receiving an injection.Consequently, a proximal direction refers to a direction pointingtowards the body of a patient receiving the injection and a proximal enddefines an end of an element that is directed towards the body of thepatient. Respectively, the distal end of an element or the distaldirection is directed away from the body of the patient receiving theinjection and opposite to the proximal end or proximal direction.

According to the invention, an auto-injector for administering a dose ofa liquid medicament comprises

a substantially cylindrical housing arranged to contain a pre-filledsyringe filled with the medicament,

a needle shroud slidably arranged with respect to the housing andadapted to rest on the skin of a patient receiving an injection,

a releasable drive means arranged within the housing that is capable of,upon release, translating the needle shroud in a proximal directiontowards a safe position and

a rotating collar rotatably arranged within the housing. The needleshroud in the safe position surrounds the injection needle after theinjection has been carried out. The rotating collar engages the needleshroud in a manner that forces the rotating collar to rotate within thehousing when the needle shroud is translated in the proximal direction.

A stopper may be arranged in the syringe barrel arranged to seal itsdistal end and to expel the dose of medicament. A coupling shroud may beslidably arranged within the housing and releasably coupled to a plungerthat is connected to the stopper. The drive means may be arrangedbetween a distal end of the housing and the coupling shroud to bias thecoupling shroud in a proximal direction towards the skin of a patientreceiving an injection.

The rotating collar creates friction to slow down a proximal movement ofthe needle shroud that rests on the skin of the patient during theinjection. The rotating collar acts as a dampening element thatalleviates the pressure exerted upon the skin of the patient by theneedle shroud that is driven by the drive means. Thus, the risk ofinjuries is reduced and, in particular, bruises may be avoided.Furthermore, the modulus of resilience of the single drive means may bechosen to be sufficiently large without having to worry about potentialinjury risks. Thus, the modulus of resilience of the drive means isadapted to reliably provide an energy supply for executing a pluralityof actions comprising, among others, the advancing and releasing of theneedle shroud, the displacement of the stopper to expel the medicamentand the decoupling of the plunger and the coupling shroud.

Preferably, the rotating collar comprises a pin that engages a helicalrecess formed into the needle shroud. The engagement of the helicalrecess and the pin forces the rotating collar to rotate around theneedle shroud when the needle shroud is translated. This dampens theproximal movement of the needle shroud and thus reduces the pressureexerted upon the skin of the patient by generating friction.

According to a possible embodiment of the invention, the needle shroudis slidable in a distal direction from an advanced position to arefracted position. In particular, the needle shroud may be slid to theretracted position by placing the auto-injector onto the skin of thepatient receiving the injection and pressing the needle shroud againstthe skin of the patient. The needle shroud in the retracted positionindicates the correct placement of the auto-injector. An activation of amechanism of the auto-injector delivering the medicament to the patientrequires the needle shroud to be positioned in the retracted position toensure that the auto-injector is properly used. The needle shroud isslidable in the proximal direction from the retracted position to thesafe position, wherein the needle shroud surrounds an injection needleof the pre-filled syringe to prevent accidental needle stick injuriesafter the injection has been carried out.

According to another possible embodiment of the invention, the drivemeans is arranged to be released by manual actuation of a releaseelement that is hinged to a lateral side of the housing. Conventionalauto-injectors are commonly activated by actuating a push button or thelike arranged at a distal end of the auto-injector. An inexperienceduser of such a conventional auto-injector may easily mistake the distalend for a proximal end of the auto-injector and thus may pierce hisfinger while trying to actuate the auto-injector. The lateralarrangement of the release element is a simple means to prevent suchaccidental needle stick injuries resulting from a misuse of theauto-injector.

Alternatively, the release element is in slidable arrangement with thehousing and may be translated with respect to the housing in theproximal direction to release the drive means. The auto-injectoraccording to this embodiment of the invention is particularly intuitiveto operate.

According to another possible embodiment of the invention, theauto-injector comprises safety means that cooperate with the needleshroud that is arranged to prevent a release of the drive means when theneedle shroud is in the advanced position and hence is not pushedagainst the skin of the patient. This mechanism avoids an early releaseof the drive means and thus a premature expelling of the medicament.Furthermore, injuries resulting from an activation of the drive meanswhen the auto-injector is not placed, or not properly placed onto theskin of the patient are reduced.

The safety means may comprise a blocking element slidably arrangedrelative to the housing. The blocking element is arranged to limit apivoting movement of the release element hinged to the lateral side ofthe housing when the needle shroud is in the advanced position. Arelease of the drive means is thus prevented. The release element isallowed to pivot about the hinge when the needle shroud is moved to theretracted position by pressing the needle shroud against the skinsurface of the patient receiving the injection.

In one possible embodiment of the invention, the safety means comprisesan elastic bushing that engages a plunger of the pre-filled syringeand/or a coupling shroud that is biased by the drive means and coupledto the plunger of the pre-filled syringe. The elastic bushing is firmlyattached to a proximal end of the housing and may engage the couplingshroud and/or the plunger to prevent an inadvertent release of the drivemeans.

In another preferred embodiment of the invention, the drive means iscapable of, upon release, driving the coupling shroud releasably coupledto the plunger from a first position in the proximal direction. Thecoupling shroud is driven by the drive means to interact with differentcomponents of the auto-injector, so that the resilient force provided bythe drive means may be used to power a variety of functions of theauto-injector. The proximal translatory movement of the coupling shroudwith respect to the housing

translates a syringe retainer receiving the pre-filled syringe in theproximal direction to expose the injection needle of the pre-filledsyringe,

depresses the plunger connected to a stopper into the syringe barrel toexpel the dose of medicament and

translates the needle shroud in the proximal direction. The couplingshroud mediates the resilient force provided by the drive means to thisvariety of different components of the auto-injector and thus allows fora compact design of the auto-injector. In particular, the auto-injectormay be powered by just a single drive means to accomplish a plurality oftasks necessary for safely carrying out the injection.

According to yet another possible embodiment of the invention, thesyringe retainer is releasably mounted to the housing. The needle shroudin the retracted position releases the syringe retainer to allow for theproximal translation of the syringe retainer with respect to thehousing. Thus, a proximal movement of the syringe retainer that inparticular inserts the injection needle into the skin of the patient isprevented until the auto-injector is correctly placed upon the skin ofthe patient and the needle shroud is pushed against the skin surfacetowards the retracted position. This prevents an inadvertent earlyrelease of the drive means.

The coupling shroud is initially in a first position, and coupled to theplunger to translate the syringe retainer proximally, whereby theinjection needle is inserted into the skin of the patient, and todepress the stopper into the syringe barrel to expel the medicament. Theplunger and the coupling shroud are decoupled from each other at theproper pre-determined second position after the medicament has beencompletely or partially delivered. The pre-determined second position isdefined by a longitudinal aperture in the housing.

According to another possible embodiment of the invention, a couplingcatch is arranged to abut against a shoulder formed to the plunger as aparticularly simple and reliable means to releasably couple the plungerto the coupling shroud. The coupling shroud is moved by the action ofthe relaxing drive means in the proximal direction and is coupled to theplunger connected to the stopper to insert the injection needle beforethe injection and to expel the medication during the injection.

The aperture formed into the lateral side of the housing at the secondposition allows the coupling catch to deflect radially outwards at thesecond position, so that the coupling shroud is decoupled from theplunger after the medicament is partially or completely delivered.

Preferably, the drive means is arranged as a single compression spring.The mechanism of the auto-injector is arranged in a manner that aplurality of functions is executed by the single drive means. Theinjection needle is inserted into the skin of the patient, the plungeris translated to expel the medicament and the needle shroud is movedproximally to provide needle safety after the injection is completed bythe action of the spring means. Conventional auto-injectors usuallycomprise a plurality of spring means to accomplish these tasks. Theauto-injector according to the invention comprises only few parts and isparticularly inexpensive to mass-produce. Consequently, theauto-injector is particularly suited as a single-use device that may bedisposed after an injection has been carried out.

The auto-injector may preferably be used for subcutaneous orintra-muscular injection, particularly for delivering one of ananalgetic, an anticoagulant, insulin, an insulin derivate, heparin,Lovenox, a vaccine, a growth hormone, a peptide hormone, a proteine,antibodies and complex carbohydrates.

Further scope of applicability of the present invention will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus, are not limitiveof the present invention, and wherein:

FIGS. 1A and 1B show two different sectional views of an auto-injectoraccording to a first embodiment of the invention with a hinged releaseelement before an injection,

FIG. 2 is an expanded sectional view of the auto-injector according tothe first embodiment, wherein the release element is blocked to preventan inadvertent release of a drive means,

FIG. 3 is an expanded sectional view of the hinged release element thatis actuated to release the drive means,

FIGS. 4A and 4B are two different sectional views of the auto-injectoraccording to the first embodiment after a drug has been delivered,

FIG. 5 is an isometric view of a needle shroud,

FIGS. 6A and 6B are two different sectional views of the auto-injectoraccording to the first embodiment after an injection has been performed,

FIGS. 7A and 7B are two different sectional views of an auto-injectoraccording to a second embodiment of the invention,

FIG. 8 is a sectional view of a distal end section of the auto-injectoraccording to the second embodiment of the invention,

FIGS. 9A and 9B are two different sectional views of an auto-injectoraccording to a third embodiment of the invention,

FIG. 10 is a sectional view of a distal end section of the auto-injectoraccording to the third embodiment of the invention.

Corresponding parts are marked with the same reference symbols in allfigures.

DETAILED DESCRIPTION

FIGS. 1A and 1B show two sectional views of an essentially cylindricalauto-injector 1 according to a first embodiment of the invention,wherein the sectional plane shown in FIG. 1A is oriented perpendicularlyto the one shown in FIG. 1B. The auto-injector 1 comprises a housing 2,a proximal needle shroud 3, a syringe retainer 4 adapted to mount andmove translatably with a pre-filled syringe 5 within the housing 2, acoupling shroud 6 slidably arranged within the housing 2 and a releaseelement 7 hinged to a lateral side of the substantially cylindricalhousing 2 of the auto-injector 1. The syringe retainer 4 includes aninwardly angled protrusion 4.2, and the syringe 5 includes a distalflange 5.1.

A single drive means 8 is arranged between the distal end of the housing2 and the coupling shroud 6 to bias the coupling shroud 6 in a proximaldirection P towards the skin of a patient receiving an injection.

According to one possible embodiment of the invention, the drive means 8is arranged as a single, conventional compression spring.

The coupling shroud 6 is releasably coupled to a plunger 9 that isconnected to a stopper 10 fluid-tightly sealing a distal end of asyringe barrel 11 containing a dose of a medicament M. An inner cavityof the syringe barrel 11 is in fluid communication with an injectionneedle 12, so that the dose of the medicament M may be expelled throughthe injection needle 12 by displacing the stopper 10 in the proximaldirection P.

Before the injection, the coupling shroud 6 abuts against a distal endof the release element 7 to releasably retain the coupling shroud 6 in afirst position I, wherein the coupling shroud 7 is located at a distalend of the housing 2. The drive means 8 is compressed, so that thecoupling shroud 6 is strongly biased in the proximal direction P.

The plunger 9 extends from the syringe barrel 11 in a distal direction Dand comprises a shoulder 9.1 of increased diameter. The coupling shroud6 comprises an inwardly protruding coupling catch 6.1 that bears againstthe shoulder 9.1 so that the plunger 9 and the coupling shroud 6 may bejointly moved in the proximal direction P by the action of the relaxingdrive means 8.

The proximal end of the needle shroud 3 is designed to be pushed againstthe skin surface of the patient during the injection. Edges of theneedle shroud 3 may thus be smoothed to avoid injuries. The needleshroud 3 is slidably arranged within the housing 2 of the auto-injector1, so that the needle shroud 3 may be pushed from an advanced positionPA shown in FIGS. 1A and 1B in the distal direction D. A biasing means13 bears against the needle shroud 3 and the housing 2 to bias theneedle shroud 3 towards the advanced position PA.

An annular rotating collar 14 engages an outer surface of the needleshroud 3. The rotating collar 14 rotates around an axis of thesubstantially cylindrical auto-injector 1 when the needle shroud 3 islongitudinally displaced in the proximal and/or the distal direction P,D. The rotating collar 14 acts as a damping means that creates frictionto slow down the movement of the needle shroud 3 and to reduce thepressure exerted onto the skin of the patient receiving the injection.

The release element 7 hinged to the housing 2 works like a see-saw: aproximal section may be pushed radially inwards, whereby the releaseelement 7 pivots about a hinge 15, so that the distal section of therelease element 7 moves radially outwards and the coupling shroud 6 isdisengaged to release the drive means 8.

The auto-injector 1 comprises safety means S that prevent an earlyrelease of the drive means 8. The safety means S ensure that the needleshroud 3 is pushed against the skin of the person receiving theinjection before the drive means 8 may be released.

According to the first embodiment of the invention, the safety means Scomprise a blocking element 16 slidably arranged with the housing 2.When the needle shroud 3 is positioned in the advanced position PA, theblocking element 16 is positioned to prevent a pivoting movement of therelease element 7 and thus a release of the coupling shroud 6. Aradially outwards protruding blocking projection 16.1 of the blockingelement 16 is located opposite to an inward protrusion 7.1 formed to therelease element 7. If the proximal section of the release element 7 ispushed inwards, the inward protrusion 7.1 abuts against the blockingprojection 16.1 to limit the pivoting movement of the release element 7,so that a release of the coupling shroud 6 and the drive means 8 isprevented.

FIG. 2 shows a proximal section of the auto-injector 1 in a sectionalview with the blocking element 16 positioned to prevent an inadvertentactuation of the hinged release element 7 to release the drive means 8.

A distal end of the needle shroud 3 is clipped to the housing 2 andretained between two inwardly protruding retaining protrusions 2.1formed into an inner surface of the housing 2. The two retainingprotrusions 2.1 are longitudinally displaced from each other to limitthe range of axial displacement of the needle shroud 3 with respect tothe housing 2. A boss 3.1 formed into an outer surface of the needleshroud 3 bears against an inner surface of the blocking element 16, sothat the blocking element 16 may move with the needle shroud 3 in theproximal direction P to deblock the release element 7.

The blocking projection 16.1 comprises a central indention that forces auser of the auto-injector 1 to perform a sequence of actions necessaryto inject the dose of the medicament M in the proper order. If therelease element 7 is pushed inwards before the needle shroud 3 is movedproximally from the advanced position PA towards a retracted position PR(see FIG. 3) by pushing the needle shroud 3 towards the skin of thepatient, the inward projection 7.1 is retained in the centralindentation of the blocking projection 16.1, so that both thelongitudinal displacement of the needle shroud 3 and the pivotingmovement of the release element 7 is blocked.

A proper sequence of actions for injecting the dose of the medicament Mis described in the following. First, the user pushes the needle shroud3 against the skin to move the needle shroud 3 distally to the retractedposition PR illustrated in FIG. 3. The blocking element 16 jointly moveswith the needle shroud 3 in the distal direction D, so that the releaseelement 7 may be manually actuated to pivot about the hinge 15, wherebythe drive means 8 are released.

Upon release of the drive means 8, the coupling shroud 6 is urged in theproximal direction P. The single and fully compressed drive means 8drives the coupling shroud 6 and the plunger 9 coupled thereto in theproximal direction P. The coupling shroud 6 first pushes the syringeretainer 4 by means of plunger 9, stopper 10 and the friction betweenstopper 10 and syringe 11 proximally to insert the injection needle 12into the skin of the patient and a first clip connection 2.2 formed intoa lateral side of the housing 2 latches to an outward protrusion 4.1 ofthe syringe retainer 4, as illustrated in more detail in FIG. 4B. Thehousing 2 includes an inward protrusion 2.9 to limit proximal movementof the syringe retainer 4 relative to the housing 2.

The syringe retainer 4 and the pre-filled syringe 5 mounted thereto isnow locked to the housing 2. The coupling shroud 6 is moved further inthe proximal direction P by the action of the relaxing drive means 8,whereby the plunger 9 is depressed into the syringe barrel 11 to expelthe dose of the medicament M contained therein through the injectionneedle 12.

FIGS. 4A and 4B show two sectional views of the auto-injector 1according to the first embodiment of the invention with the plunger 9fully depressed within the syringe barrel 11. The dose of the medicamentM has been delivered beneath the skin of the patient. The couplingshroud 6 is located in an intermediate second position II. The drivemeans 8 is not yet completely discharged and biases the coupling shroud6 in the proximal direction P. The shoulder 9.1 engages a ramp of thecoupling catch 6.1 to deflect the coupling catch 6.1 in a radial outwarddirection. An aperture 2.3 is formed into the housing 2 to allow for aradial outward deflection of the coupling catch 6.1, so that thecoupling catch 6.1 overcomes the shoulder 9.1 decoupling the couplingshroud 6 from the plunger 9.

In a possible embodiment of the invention, the aperture 2.3 defining thesecond position II is located at a longitudinal position along thehousing 2 that allows for a full depression of the plunger 9 completelyemptying the syringe barrel 11 before the plunger 9 is decoupled fromthe coupling shroud 6.

Alternatively, the aperture 2.3 defining the second position II may belocated at a longitudinal position along the housing 2 that allows foran adjustment space accounting for manufacturing tolerances. Theadjustment space is dimensioned as to allow for a reliable decoupling ofthe plunger 9 from the coupling shroud 6 even if the parts constitutingthe auto-injector 1 comprise mismatch in mould or are slightlymisaligned. In this alternative embodiment, the dose of the medicament Mmay or may not be completely expelled before the plunger 9 is decoupledfrom the coupling shroud 6.

The retaining protrusions 2.1 are elastically supported and may bedeflected radially outwards to release the needle shroud 3. The couplingshroud 6 engages a ramp of the retaining protrusions 2.1 and splays theretaining protrusions 2.1 outwards, whereby the needle shroud 3 isreleased and allowed to move proximally from the retracted position PRtowards an extended safe position PS.

The drive means 8 is still partially loaded when the coupling shroud 6is located in the second position II. In a possible embodiment of theinvention the biasing force of the drive means 8 exerted on the couplingshroud 6 in the second position II is about 10 N.

The coupling shroud 6 bears against a distal end of the needle shroud 3,so that the needle shroud 3 may be moved to the safe position PS by theaction of the further relaxing drive means 8. As the biasing forceexerted onto the needle shroud 3 by the drive means 8 may be relativelylarge and could even bruise the patient, the rotating collar 14 isarranged within the housing 2 to partially absorb the excess energy ofthe drive means 8 and slow down the proximal movement of the needleshroud 3 by generating friction.

FIG. 5 shows an isometric view of the needle shroud 3. A helical recess3.2 is formed into a tubular proximal section 3.3 of the needle shroud3. The proximal section 3.3 of the needle shroud 3 is inserted into theannular rotating collar 14, wherein a pin 14.1 formed to an innersurface of the rotating collar 14 protrudes into the helical recess 3.2as shown in FIG. 6A. The linear translatory movement of needle shroud 3towards the safe position PS thus causes the rotating collar 14 torotate within the housing 2 around the axis of the auto-injector 1.

FIGS. 6A and 6B show two different sectional views of the auto-injector1 according to the first embodiment of the invention after the injectionhas been performed. The needle shroud 3 is permanently locked to thesafe position PS by a second clip connection 2.4 formed into the housing2. The needle shroud 3 surrounds the injection needle 12 and extends asuitable distance proximally beyond the needle tip to avoid accidentalneedle stick injuries after the auto-injector 1 has been used.

FIGS. 7A and 7B show two different sectional views of an auto-injector 1according to a second embodiment of the invention before the injection.The sectional plane shown in FIG. 7A is oriented perpendicularly to thesectional plane shown in FIG. 7B.

The needle shroud 3 of the auto-injector 1 according to the secondembodiment substantially extends over the axial length of the housing 2.Before the injection, the needle shroud 3 is mounted to the housing 2 bythe retaining protrusions 2.1 that protrude into orifices formed into alateral side of the needle shroud 3. The orifices comprise alongitudinal length that allows the needle shroud 3 to be slid from theadvanced position PA to the retracted position PR.

A retaining catch 2.5 (e.g. a flexible arm) is formed to an innersurface of the housing 2 and protrudes through an opening formed intothe needle shroud 3 to releasably mount the syringe retainer 4 retainingthe pre-filled syringe 5. The retaining catch 2.5 comprises a bevelledramp and is deflectable in a radial outward direction. The retainingcatch 2.5 latches to the outward protrusion 4.1 formed to the outersurface of the syringe retainer 4 when the needle shroud 3 is in theadvanced position PA.

The needle shroud 3 abuts against the bevelled ramp of the retainingcatch 2.5 when the needle shroud 3 is moved from the advanced positionPA in the distal direction D, whereby the retaining catch 2.5 isdeflected in a radial outward direction and disengages the outwardprotrusion 4.1, so that the syringe retainer 4 may be moved in theproximal direction P.

The release element 7, shown in more detail in FIG. 8, is arranged as apush button and mounted to a distal end of the housing 2. The releaseelement 7 may be pushed in the proximal direction P to release the drivemeans 8 when the needle shroud 3 is in the retracted position PR,whereas the release element 7 and thus the release of the drive means 8is blocked when the needle shroud 7 is in the advanced position PA.

According to the second embodiment of the invention, the safety means Sthat prevent the early release of the drive means 8 comprises clips 2.6that may deflect in a radial outward direction and a bushing 17 lockingthe plunger 9 before use of the auto-injector 1.

Before the auto-injector 1 is used, the clips 2.6 formed to the housing8 latch to the release element 7. (See FIG. 7B) The clips 2.6 block themovement of the release element 7 in the proximal direction P, so that amanual actuation of the release element 7 is prevented as long as theneedle shroud 3 is in the advanced position PA. A distal movement of therelease element 7 is blocked by a first detent 2.7 engaging an innersurface of the release element 7.

The clip 2.6 comprises a ramp that the needle shroud 3 engages whenpushed distally from the advanced position PA to the refracted positionPR, whereby the clip 2.6 is deflected radially outwards to disengage theneedle shroud 3. The release element 7 may be pushed in the proximaldirection P when the needle shroud 3 is in the retracted position PR.

The plunger 9 comprises a distal end 9.2 of increased diameter that isretained in the bushing 17 firmly attached to a distal end of thehousing 2. The bushing 17 comprises an inner surface corresponding tothe distal end 9.2 of the plunger 9 that engages the distal end 9.2 in alocked position L to lock the plunger 9 and the coupling shroud 6coupled thereto to the housing 2 before use of the auto-injector 1. Thebushing 17 abuts radially against an annular inner collar 7.2 of therelease element 7 in the locked position L shown in FIGS. 7A and 7B. Aradial outward deflection of the bushing 17 releasing the plunger 9 isthus prevented.

FIG. 8 shows a sectional view of a distal end section of theauto-injector 1 according to the second embodiment of the invention. Theneedle shroud 3 is located in the retracted position PR and the releaseelement 7 is pushed in the proximal direction P, so that the bushing 17disengages the annular inner collar 7.2 of the release element 7. Thebushing 17 is positioned in an unlocked position U and may deflectoutwardly to release the plunger 9.

Furthermore, the bushing 17 acts as a counter bearing for the drivemeans 8 bearing against the bushing 17 in the distal direction D.

FIGS. 9A and 9B show two different sectional views of an auto-injector 1according to a third embodiment of the invention, wherein the releaseelement 7 is arranged as an outer sleeve extending over a substantiallength of the auto-injector 1.

According to the third embodiment of the invention, the safety means Sthat prevent the early release of the drive means 8 comprise clips 2.6,second and third detents 2.8, 7.3, a locking catch 6.2 formed to thecoupling shroud 6 and the bushing 17 that comprises an inner sleeve 17.1receiving a lug 7.4, wherein the locking catch 6.2 latches to a collar17.2 of the inner sleeve 17.1.

The release element 7 of the third embodiment is gripped by a user toperform the injection. When the needle shroud 3 is in the advancedposition PA, the proximal displacement of the release element 7 isblocked by the clips 2.6 in a similar manner as in the second embodimentdescribed herein above.

Additionally, the release element is releasably retained in positionbefore the injection by the second and the third detents 2.8, 7.3respectively formed to an outer surface of the housing 2 and to an innersurface of the release element 7, wherein the second and third detents2.8, 7.3 comprise correspondingly shaped ramps facing each other.

The bushing 17 of the third embodiment comprises the inner sleeve 17.1that receives the lug 7.4 formed to an inner surface of the releaseelement 7. A proximal end of the lug 7.4 snugly fits in the centralaperture of the inner sleeve 17.1, so that an inward deflection of theinner sleeve 17.1 is prevented.

The inner sleeve 17.1 comprises a collar 17.2. An inwardly protrudinglocking catch 6.2 of the coupling shroud 6 latches to the collar 17.2before use of the auto-injector 1 to releasably retain the couplingshroud 6 in the first position I.

FIG. 10 shows a sectional view of a distal end section of theauto-injector 1 according to the third embodiment of the invention. Therelease element 7 is actuated and moved in the proximal direction P. Theproximal end of the lug 7.4 disengages the inner sleeve 17.1 of thebushing 17, so that the inner sleeve 17.1 may bend radially inwards,whereby the locking catch 6.2 disengages the collar 17.2 and releasesthe coupling shroud 8 and the drive means 8.

The invention claimed is:
 1. A method comprising: disposing a syringeretainer in a distal position in a housing such that an outwardprotrusion of the syringe retainer is engaged with a flexible arm of thehousing to releasably hold the syringe retainer in a fixed axialposition relative to the housing; disposing a syringe within the syringeretainer such that a proximal end of a body of the syringe is engagedwith an inwardly angled protrusion of the syringe retainer that isdisposed at a proximal end of the syringe retainer, the inwardly angledprotrusion of the syringe retainer being configured to limit proximalmovement of the syringe relative to the syringe retainer, wherein, withthe syringe disposed within the syringe retainer, a distal end of thesyringe extends distally beyond a distal end of the syringe retainer anda distal flange of the syringe is distally spaced apart from the syringeretainer; applying an axial force to a beveled ramp of the flexible armthereby deflecting the flexible arm outward such that the outwardprotrusion of the syringe retainer becomes disengaged from the flexiblearm of the housing allowing the syringe retainer and the syringedisposed in the syringe retainer to move proximally relative to thehousing; and proximally moving the syringe retainer and the syringewithin the housing from the distal position to a proximal position inwhich the syringe retainer is engaged with an inward protrusion of thehousing to limit proximal movement of the syringe retainer relative tothe housing.
 2. A method comprising: disposing a syringe retainer in adistal position in a housing such that an outward protrusion of thesyringe retainer is engaged with a flexible arm of the housing toreleasably hold the syringe retainer in a fixed axial position relativeto the housing; applying an axial force to a beveled ramp of theflexible arm thereby deflecting the flexible arm outward such that theoutward protrusion of the syringe retainer becomes disengaged from theflexible arm of the housing allowing the syringe retainer and a syringedisposed in the syringe retainer to move proximally relative to thehousing; and proximally moving the syringe retainer and the syringewithin the housing from the distal position to a proximal position inwhich the syringe retainer is engaged with an inward protrusion of thehousing to limit proximal movement of the syringe retainer relative tothe housing.
 3. The method of claim 2, wherein the housing, the syringeretainer, and the syringe are components of an auto-injector.
 4. Themethod of claim 2, wherein proximally moving the syringe retainer withinthe housing from the distal position to the proximal position comprisesengaging the syringe retainer with the inward protrusion of the housingto proximally restrain the syringe retainer within the housing such thatfurther proximal movement of the syringe retainer relative to thehousing is prevented.
 5. The method of claim 2, wherein disposing thesyringe within the syringe retainer comprises engaging an inwardlyangled protrusion of the syringe retainer that is disposed at a proximalend of the syringe retainer with a proximal end of a body of thesyringe.
 6. The method of claim 5, wherein engaging the inwardly angledprotrusion of the syringe retainer with the proximal end of the body ofthe syringe axially retains the syringe relative to the syringe retainersuch that proximal movement of the syringe relative to the syringeretainer is prevented.
 7. The method of claim 5, wherein, with thesyringe disposed within the syringe retainer, a distal end of thesyringe extends distally beyond a distal end of the syringe retainer anda distal flange of the syringe is distally spaced apart from the syringeretainer.
 8. The method of claim 7, wherein the outward protrusionextends radially outward from an outer surface of the syringe retainerand, with the syringe disposed within the syringe retainer, the outwardprotrusion extends radially beyond the distal flange of the syringe. 9.The method of claim 2, comprising axially moving a needle shroudrelative to the housing to apply the axial force to the beveled ramp ofthe flexible arm to deflect the flexible arm outward.
 10. The method ofclaim 2, wherein disposing the syringe retainer in the distal positionin the housing such that the outward protrusion of the syringe retaineris engaged with the flexible arm of the housing comprises engaging theoutward protrusion with a surface of the flexible arm.
 11. The method ofclaim 2, wherein deflecting the flexible arm outward comprisesdeflecting the flexible arm such that a portion of the flexible armextends beyond an outer surface of the housing.
 12. The method of claim2, wherein a distal end of syringe retainer is positioned proximal to adistal end of the housing when the syringe retainer is disposed in thedistal position.
 13. The method of claim 2, wherein a distal end of adistal flange of the syringe is positioned proximal to a distal end ofthe housing when the syringe retainer is disposed in the distalposition.
 14. An auto-injector comprising: a housing comprising (i) aflexible arm integrally formed with a cylindrical body of the housingand having a beveled ramp and (ii) an inward protrusion integrallyformed with the cylindrical body of the housing; a syringe containing amedicament; and a syringe retainer retaining the syringe, the syringeretainer having an outer surface and an outward protrusion extendingradially outward from the outer surface, the syringe retainer disposedwithin the housing and being axially slidable within the housing from adistal position in which the flexible arm of the housing engages theoutward protrusion of the syringe retainer to restrain axial movement ofthe syringe retainer relative to the housing, to a proximal position inwhich the outer surface of the syringe retainer engages the inwardprotrusion of the housing to limit further proximal movement of thesyringe retainer relative to the housing, wherein the auto-injector isconfigured such that applying an axial force to the beveled ramp of theflexible arm deflects the flexible arm outward such that the outwardprotrusion of the syringe retainer becomes disengaged from the flexiblearm of the housing allowing the syringe retainer and the syringedisposed in the syringe retainer to move proximally relative to thehousing from the distal position to the proximal position, wherein thesyringe retainer is sized such that a distal end of the syringe extendsdistally beyond a distal end of the syringe retainer and a distal flangeof the syringe is distally spaced apart from the syringe retainer. 15.The auto-injector of claim 14, wherein an axial position of the inwardprotrusion of the housing defines an axial length that an injectionneedle of the syringe extends proximally beyond the housing when thesyringe retainer is disposed in the proximal position.
 16. Theauto-injector of claim 14, wherein the inward protrusion of the housingis located proximally of the flexible arm.
 17. The auto-injector ofclaim 14, wherein the outward protrusion is located on a distal portionof the syringe retainer.
 18. The auto-injector of claim 14, wherein theoutward protrusion is configured to engage a surface of the flexible armwhen the syringe retainer is disposed in the distal position.
 19. Theauto-injector of claim 14, wherein the flexible arm is configured todeflect outward such that a portion of the flexible arm extends beyondan outer surface of the housing.
 20. The auto-injector of claim 14,wherein the beveled ramp extends inwardly from a surface of the flexiblearm.
 21. The auto-injector of claim 14, wherein an axial distancebetween the distal flange of the syringe and a distal end of the syringeretainer is larger than an axial width of the inward protrusion of thehousing.
 22. The auto-injector of claim 14, wherein a distal end of thesyringe retainer is positioned proximal to a distal end of the housingwhen the syringe retainer is disposed in the distal position.
 23. Theauto-injector of claim 22, wherein a distal flange of the syringe ispositioned proximal to a distal end of the housing when the syringeretainer is disposed in the distal position.
 24. The auto-injector ofclaim 14, wherein an outer surface of the flexible arm substantiallyaligns with an outer surface of the cylindrical body when the syringeretainer is in the proximal position.
 25. The auto-injector of claim 14,wherein the housing has a unitary construction.
 26. The auto-injector ofclaim 14, wherein the flexible arm of the cylindrical body is a firstflexible arm, and the cylindrical body comprises a second flexible armhaving a beveled ramp.
 27. The auto-injector of claim 26, wherein thefirst and second flexible arms are disposed radially opposite to eachanother.
 28. The auto-injector of claim 14, comprising a needle shroud,the auto-injector being configured such that axially moving the needleshroud relative to the housing applies the axial force to the beveledramp of the flexible arm to deflect the flexible arm outward.
 29. Theauto-injector of claim 28, wherein the needle shroud is configured toretract from an extended position in which a proximal end of the needleshroud extends proximally beyond a proximal end of an injection needleof the syringe, to a retracted position in which the proximal end of theinjection needle extends proximally beyond the proximal end of theneedle shroud.